(1) Field of the Invention
This invention relates to a mold clamping mechanism in an injection molding machine, and particularly to a mold-thickness adjusting apparatus in a direct pressure type mold clamping mechanism.
(2) Prior Art
In a mechanism in which a clamping plate is movably provided between a pair of fixed plates, a clamping ram of a clamping cylinder provided on one fixed plate are connected, and a mold dividedly attached to the other fixed plate and the clamping plate is directly clamped by the clamping ram, if the clamping cylinder is designed to be lengthy, the clamping can be always carried out positively according to a mold thickness without the particular provision of a mold-thickness adjusting apparatus.
However, if the moving dimension of a piston within the clamping cylinder is large, it takes time for movement of the clamping ram to make it difficult to open and close the mold at high speeds. For this reason, even in the case of the direct-pressure type, mold-thickness adjusting means is usually provided.
According to the conventional mold-thickness adjusting means, a standard mold-thickness is determined according to the dimension of length of the clamping cylinder so that when the mold is thinner than the standard mold-thickness, a wedge or the like is engaged to increase the thickness.
Alternatively, a proposal has been made in which a clamping ram and a clamping plate are threadedly connected by a rotatable joint, so that the clamping plate may be moved back and forth by the rotation of the joint to effect the adjustment of mold-thickness. In this proposal, however, the clamping force is concentrated on the threaded portion of the joint to make it difficult to rotate the joint at the time of the mold-thickness adjustment due to the close contact of mutual threads. In addition, parts are often damaged thus failing to be useful for the mold-thickness adjustment, which is unsuitable for practical use.